The objective of this research program is to obtain basic information leading to an improved understanding of enzymatically catalyzed glycosylation, and of the relationship of glycoside hydrolases to glycosyl transferases. The glycosylation process effected by these enzymes is of central biological importance as the means whereby all of the varied complex saccharides of living forms are synthesized from (and broken down to) smaller sugar components. Our goal of advancing the levels of understanding of catalysis by this wide range of enzymes will be approached by the use of a unique, new experimental method. This consists of the study of glycosylation reactions that take place with glycosyl (but nonglycosidic) substrates. Such reactions will be used to probe the catalytic scope and mechanism of a number of highly purified, model enzymes that are considered to be well characterized on the basis of their actions on glycosidic substrates. Specific glycosyl fluoride substrates will be used to elucidate the newly recognized capacity of classic endo-glucan hydrolases to catalyze predominantly nonhydrolytic or polymerative reactions. We will also use the extraordinary ability of exo-alpha-glucanases to attack both alpha-and beta-anomers of appropriate glycosyl fluorides to determine whether, as appears likely, these configuration-inverting enzymes have dual modes of catalytic activity and not the single (hydrolytic) mode long throught to characterize such enzymes. In addition, glycals and newer enolic glycosyl substrates that lack alpha- or beta anomeric configuration will be used to generate new information on the catalytic mechanism of enzymes known to cause reactions that always retain (or always invert) substrate configuration. We will also determine whether these enolic compounds, which tend to form glycosyl carbonium ions when protonated at the double bond, are substrates for enzymes such as sucrose phosphorylase that are models of action by a double nucleophilic displacement mechanism.